Juvenile Tyrannosaurus rex Feeding Traces Identified

Juvenile Tyrannosaurs Fed on Large Hadrosaurs Too

Scientists have identified tooth marks preserved in the tail bone of a duck-billed dinosaur as having been made by a sub-adult Tyrannosaurus rex. The researchers conclude that late-stage juvenile and subadult Tyrannosaurs were already feeding on the same types of large-bodied prey as adult animals, despite lacking the bone crushing jaws typical of a fully-grown, mature T. rex.

Writing in the academic journal PeerJ, the researchers Joseph E. Peterson and Karsen N. Daus (University of Wisconsin), suggest that this study helps scientists to better understand the diets of Tyrannosaurs and the ecological role they played as predators in Late Cretaceous ecosystems. Biostratigraphically, the victim’s fossils relate to sediments were Edmontosaurus fossils are found, so the prey has been tentatively identified as an Edmontosaurus.

Evidence of a Subadult T. rex Feeding on a Hadrosaur (Edmontosaurus)

The punctured tail bone indicating feeding by a sub-adult T. rex.

Picture Credit: PeerJ

The picture above shows views of the punctured tail bone (BMR P2007.4.1.) in (A) anterior view, (B) posterior view and (C) ventral view. Images (D and E) are close-up views of the punctures identified on the bottom portion of the caudal vertebra.

Theropod Feeding Traces

Palaeontologists have identified numerous examples of Theropod dinosaur feeding traces and tooth marks. Such evidence provides information on predator/prey interactions, feeding behaviours and direct evidence of cannibalism in the Dinosauria. However, in order to determine the meat-eating dinosaur that fed, causing the marks, it is important that the biostratigraphy is known and the approximate likely growth stage of the animal feeding. The researchers state that currently, most recorded Theropod feeding traces and bite marks are attributed to fully-grown, adult animals, but in this study, the bite marks were compared to various jaws of different aged T. rex specimens and it was concluded that the best fit for the feeding traces came from the maxilla of a late-stage juvenile T. rex estimated to be around 11-12 years old. The dimensions and spacings on the caudal vertebra best matched the maxillary teeth of specimen number BMR P2002.4.1, a late-stage juvenile T. rex.

A Computer Generated Image Mapping the Feeding Traces

Identifying the bite marks on the tail bone of a Hadrosaur. The dimensions and spacings on the tail bone best matched the maxillary teeth (upper jaw) of BMR P2002.4.1, a late-stage juvenile Tyrannosaurus rex.

Picture Credit: PeerJ

Hunting or Scavenging?

While bite marks resulting from active predation cannot easily be distinguished from post-mortem feeding traces, the position of the punctures in the Hadrosaur tail bone suggest that the duck-billed dinosaur was already lying on its side and therefore it can be concluded that the traces come from post-mortem consumption. The researchers propose that further identification of Tyrannosaur feeding traces coupled with experimental studies of the biomechanics of Tyrannosaur bite forces from younger ontogenetic stages may reveal dynamic dietary trends and ecological roles of Tyrannosaurus rex throughout the animal’s life cycle.

Furthermore, this evidence suggests that late-stage juvenile Tyrannosaurs, at least in part, had a similar diet to the adult animals.